jobjects have to be compared with env->IsSameObject()
and each Activity needs its own Window instance.
The GtkWindow is still shared between all Activities
Adds a special treatment for the main Looper to not block in java code,
but instead return to glib managed thread loop. Timeouts in the mainloop
are now handled using g_timeout_add_full().
Also defer Activity construction, so that every thing is set up properly
when the constructor runs.
NOTE: the main addition in this commit is WIP support for apps which
render on an EGL surface obtained using ANativeWindow_fromSurface
currently, this EGL surface is obtained by creating a 700x700 pixel
window with GLFW (the 700x700 size is hardcoded in several places)
and only Wayland is supported
ideally, we'd want to use a wayland subsurface to position the EGL
surface above the Surface widget it's associated with (and do
whatever for X11)
